The invention concerns an apparatus for feeding a suspension of a solid phase in a liquid phase by a continuous or trickle flow to a disc-type rotary filter, which makes it possible for the beginning of the filtration step to be maintained at the maximum capacity of the filter which is controlled by the distributor for regulating the various steps for separation of the phases, comprising filtration, draining and removal of the solid matter.
It has long been known to effect separation, by filtration, of a continuous, liquid or gaseous phase and a dispersed, solid or liquid phase, initially forming a suspension which is produced for example by the operation of attacking an ore.
For that purpose, the suspension is taken over a carrier such as a grid, cloth, membrane, etc. on which the solid particles are deposited, forming a cake of varying thickness, while the liquid phase which constitutes the filtrate passes through the filtration cloth and is then collected by any collecting means.
Depending on the characteristics of the suspensions to be filtered such as for example the concentration of dry matter, the dimensions of the solid materials, suitability for separation, the corrosiveness of the medium, and the degree of classification required, the man skilled in the art is required to choose a suitable piece of equipment from the many different technologies which are available on the market.
Among the filtration processes which are disclosed in the specialist literature, one is very often used and appreciated in regard to separating the liquid and solid phases of suspensions which result from attacking ores using hydrometallurgical processes: the filtration process in question uses disc-type rotary filters such as those which are described for example in "Chemical Engineer's Handbook", page 19-79, by John H. Perry, edition No. 5, McGraw Hill Book Company, 1973.
As described therein, disc-type rotary filters comprise a plurality of discs which are fixed perpendicularly to a hollow horizontal shaft and which are formed by ducts in which various effects are produced such as a suction effect, a blowing effect and so forth. Each disc is formed by a plurality of independent sectors which are provided with wire gauze portions and/or textile filter bags, which are connected to the above-mentioned hollow horizontal shaft.
In the filtration operation, the discs bearing their sectors dip into a trough which contains the suspension to be filtered, the solid phase being caused to cling to the filter cloths by a suction effect while the separated liquid phase flows away in the collectors of the horizontal shaft which is provided with at least one distributor arrangement, by means of connections between each sector and the shaft itself. The solid phase which is disposed on the filter cloth is then drained when it passes into the free air and is then removed by blowing air in a counter-flow mode through the filtering surfaces.
Now, it is well known that a filtration process of that kind can no longer operate (to its full extent) once the lowest useful height of filling of the trough corresponds to insufficient immersion of the surface of a disc. That situation gives rise to a breakdown in the suction effect applied to the liquid phase through the filter medium of the sector, which jeopardizes separation of the two phases and which must be combated by quickly raising the level of the suspension in the trough.
Hence all the above-indicated disadvantages led the applicants to study and design an industrial apparatus for feeding disc-type rotary filters with a suspension, which makes it possible for the beginning of the filtration step to be maintained at the maximum capacity of the filter and to effect separation of the phases, filtration and draining, with a useful height in regard to filling of the trough, which is even lower than the lowest useful height in regard to filling of the trough.